Duncan Shimmer Glazes - SH 508 - Ruby - 4 Ounce Jar Duncan Shimmer Glazes features a sophisticated palette that marries rich color with concentrated sparkle. Perfect for all-over shimmer or for adding beautiful accents to your glaze and underglaze projects. Shimmer Glazes are nontoxic and safe for all ages to use; they're even safe to decorate dinnerware with. Shimmer Glazes are a low-fire glaze family and should be fired to cone 06. Overglaze compatible. AP Certified Non-Toxic. Food Safe. Made in USA.